This invention relates to a cathode ray tube mounting structure, and more particularly relates to a composite mounting structure integral with implosion-protective means.
Cathode ray tubes basically include a phosphor screen, at least one gun comprising an electron emitting cathode and one or more associated electrodes for focusing the emitted electrons into beams and directing the beams to the screen to excite the phosphors thereon, all in an air-evacuated glass envelope. Such envelope is normally comprised of a neck portion, containing the gun assembly, a funnel portion and a faceplate panel including a peripheral sidewall or skirt frit-sealed to the funnel. The screen is generally formed directly on the interior surface of the faceplate, and the gun is oriented along an axis normal to screen center, the so-called Z axis.
The panel skirt is commonly fitted with "implosion protection" means such as a steel tension band, to lessen the hazards surrounding tube breakage due, for example, to severe mechanical or thermal shock.
While the tube designer would prefer to have the panel skirt sidewalls parallel to the Z axis of the tube, in practice the panel is manufactured with a slight outward tilt of the skirt (for example, from 1.degree. to 3.degree.) in order to facilitate removal of the panel from the glass forming mold. This of course results in the tension band being placed on a sloping surface which Induces undesirable slippage. In some cases; a relatively thin fiber-reinforced double-sided adhesive tape has been used under the tension band to alleviate this slippage problem.
However, the tension band also often serves another purpose of providing mechanical support for tube mounting brackets or "ears" mounted at the corner regions of the panel skirt. The base portions of these generally L-shaped brackets are sometimes welded to the outer surface of the tension band (see, for example, U.S. Pat. No. 4,214,142), but are also often placed under the tension band (see, for example, U.S. Pat. Nos. 4,222,075 and 4,210,935).
When placed under the tension band, the ear bases aggravate the slippage problem, not only because they reduce the contact area between the panel skirt and the tension band, but also because their contour does not exactly fit the contour of the skirt in the corner regions. This latter condition sometimes creates a "skate effect" in which only the edges of the base are in contact with the glass, resulting in minimal resistance to slippage.
Of course, while this slippage problem could be significantly alleviated by welding the ears to the outside of the tension band, as taught in the prior art, such an approach would require complex jigging fixtures and welding equipment to obtain accurate positioning and secure attachment of the ears to the band in the desired corner locations. Thus, the tube designer is in search of a more cost effective method of alleviating the band slippage problem.
Accordingly, it is an object of the present invention to provide for a cathode ray tube mounting structure which allows the securing of the mounting brackets or ears directly on the skirt of the face panel under the tension band. It is a further object of the invention to provide for a composite mounting structure in which slippage of both the tension band and mounting brackets is substantially alleviated.